import math

def count_prime_factor(N):
    if N == 1:
        return 0
    ret = 0
    tmp = N
    c = int(math.sqrt(N)) + 1
    for n in range(2, c):
        while tmp % n == 0:
            tmp = tmp // n
            ret += 1
        if tmp == 1:
            break
    if tmp != 1:
        ret += 1
    if ret:
        return ret
    else:
        return 1


def count_divisor(N):
    ret = 0
    c = int(math.sqrt(N))+1
    for i in range(1, c):
        if N % i == 0:
            ret += 1
            if N != i * i:
                ret += 1
    return ret

N, K = map(int, input().split())
max_d = 0
ans = 0
for n in range(1, N):
    gcd = math.gcd(N, n)
    if count_prime_factor(gcd) >= K:
        d = count_divisor(n)
        if max_d < d:
            max_d = d
            ans = n
print(ans)